The electromechanical responses in ferroelectric oxides are governed by the interactions between point defects and local polarization structures, where defect-induced internal fields can strongly modify domain switching behavior. While the effects of defect type and concentration on macroscopic properties have been widely explored, the role of defect spatial correlation in mediating local structural heterogeneity and collective polarization switching remains poorly understood. Here, combined electrical transport, local-structure, and atomic-scale polarization analyses reveal a reversible transition between correlated and dispersed defect states in ${\mathrm{BiFeO}}_3\text{–}{\mathrm{BaTiO}}_3$ ceramics. Quenching above the Curie temperature freezes a dispersed defect configuration, whereas slow cooling or annealing restores correlated defect-dipole states. The correlated state generates strong internal fields, fragmenting polar domains and suppressing cooperative switching, while the dispersed state weakens defect pinning, promotes a continuous polar network, and enables enhanced electromechanical response. These results show that defect spatial correlation can serve as a thermally programmable structural parameter for ferroelectric domain engineering, providing a strategy for the design of high-performance ferroelectric materials.

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• Defects
• Electric polarization
• Ferroelectricity
• Piezoelectricity